The process of forming articles by clay slip casting is a very old process which is still used to form numerous articles, in particular substantially all ceramic sanitary articles of complex shape with hidden surfaces, and is ideal for forming such shapes.
This process is based on the fact that the mould comprises impression surfaces, formed with porous permeable material, onto which an aqueous suspension of clay material or the like is fed, preferably under pressure.
The water of the suspension, preferably aided by applied pressure, filters through the impression surface whereas the solid particles, having greater dimensions than the pores, are intercepted by the surface itself; consequently a layer of wet pasty material deposits on the surface and is left to dry, after which it is extracted from the mould.
The material used to construct those mould elements presenting the impression surfaces is therefore a porous material which enables the water to filter from the impression cavity through the body of the mould. The most traditional material is plaster-based; however recently a technology has been developed based on moulds constructed with synthetic resin of adequate porosity characteristics, which present the advantage of greater robustness and longer life, and also enable shorter forming cycles to be achieved.
An object of this invention is to improve the drainage systems provided inside moulding elements for facilitating and accelerating, during the formation of the article, the evacuation of the fluid in which the solid material particles are suspended.